fix: add deprecation warning for LegacyAdapter

lib/minimap.js

@@ -5,7 +5,6 @@ import DecorationManagement from './mixins/decoration-management'
 
 import { Emitter, CompositeDisposable } from 'atom'
 import StableAdapter from './adapters/stable-adapter'
-import LegacyAdapter from './adapters/legacy-adapter'
 
 let nextModelId = 1
 
@@ -209,6 +208,9 @@ export default class Minimap {
     if (atom.views.getView(this.textEditor).getScrollTop != null) {
       this.adapter = new StableAdapter(this.textEditor)
     } else {
+      // TODO remove LegacyAdapter in the next major version
+      atom.notifications.addWarning("LegacyAdapter of Minimap is deprecated and will be removed in the next major version. Please upgrade Atom to the latest version.")
+      const LegacyAdapter = require('./adapters/legacy-adapter')
       this.adapter = new LegacyAdapter(this.textEditor)
     }